1. Technical Field
The present invention relates to a technology of outputting (e.g., displaying and printing) a color image based on image data.
2. Related Art
As apparatuses (image output apparatuses) capable of outputting color images, various apparatuses such as color monitors, projectors, or printing apparatuses are provided in these days. Further, regarding apparatuses (image data generating apparatuses) for generating color image data, there are provided various apparatuses such as digital still cameras or digital video cameras, and further, it becomes also possible to generate color image data on computers using various application programs.
Here, the range (hereinafter referred to as “color gamut of apparatuses” in some cases) of the colors the image output apparatuses can reproduce is not necessarily the same between the image output apparatuses. Further, the range (hereinafter referred to as “color gamut of image data” in some cases) of the colors the color image data can deal with is also not necessarily the same between the image data generation apparatuses or between the application programs. Therefore, the case in which a color the color image data intends to represent cannot be reproduced by a certain image output apparatus (i.e., the color exists out of the color gamut of the image output apparatus) could occur. Further, in such a case, there is required an operation of executing a conversion on the color image data so that the range (hereinafter referred to as “color gamut of an image” in some cases) of the colors included in the color image data falls within the color gamut of the image output apparatus. Such an operation may be called color gamut mapping.
It should be noted that the entire range of the color gamut (i.e., the color gamut of the image data) the color image data can deal with is not necessarily used on a constant basis. Therefore, there exists the color image data in which only the colors within the color gamut (i.e., the color gamut of the apparatus) the image output apparatus can reproduce. Regarding such color image data, it is preferable to directly reproduce the colors the color image data intends to represent. Therefore, there has been proposed a technology intending that the range (i.e., the color gamut of the image) of the colors used in the color image data is searched by analyzing the color image data, and then the color gamut of the image and the color gamut of the image output apparatus are compared, thereby appropriately converting the color image data to display the color image. Further, it is also proposed that, in order for making it possible to quickly display a color image, the color image data is previously analyzed to obtain the color gamut of the image, and then the result is appended to the color image data as metadata (High-Definition Multimedia Interface, Specification Version 1.3a, Nov. 10, 2006, Appendix E).
However, there arises a problem that a large amount of work is required for analyzing the color image data to search the range (i.e., the color gamut of the image) of the colors used in the image data. Therefore, there has been requested development of the technology capable of simply and easily determining the color gamut of the image based on the color image data.